Holography is known as a technique that allows a three-dimensional image to be recorded and later reproduced. Specifically, coherent light is split into two light beams by a beam splitter, and then one light beam is directed onto an object and light reflected from the object (i.e., object light) illuminates onto a recorded medium, while the other light beam (i.e., reference light) directly illuminates to the recorded medium. Under this situation, the object light and the reference light interfere with each other, thereby causing interference fringes on the recording medium, and thus the interference fringes are recorded on the recording medium. The interference fringes recorded on the recording medium may be called a “hologram.” In a case where reproduction light which is the same as the reference light is illuminated on the recording medium which records the hologram, the reference light is diffracted by the hologram so that the optical wavefront of the reflected light which reaches the recording medium from an original object at the time when recording the hologram can be reproduced, and, as a result of this, images which possess three-dimensional characteristics of the original object can be observed.
In recent years, through the use of holography, holographic image displays for reproducing three-dimensional moving images have been studied. An example of a holographic image display is one which is directed to controlling a spatial modulation device in accordance with a video signal of a hologram derived from an object. It is known that a liquid crystal matrix having the characteristics of high-speed response and high definition can be used as a spatial modulation layer of such a spatial modulation device. Such a matrix allows a hologram (i.e., interference fringes) to be formed on a screen in real-time in accordance with a video signal, and when the hologram on the screen is illuminated with reproduction light, a three-dimensional image of the object can be reproduced.